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NGC2264CXO - NGC 2264 Chandra X-Ray Point Source Catalog

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Overview

The NGC 2264 Chandra X-Ray Point Source Catalog contains the results of a Chandra observation of a field in the NGC 2264 star-forming region. The observation was made with Chandra's Advanced CCD Imaging Spectrometer imaging array (ACIS-I) on 2002 February 9, and has an exposure time of 48.1 ks. The catalog contains 263 sources, and includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. The authors found 41 variable sources, 14 of which have a flare-like light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main sequence stars with ages younger than 3 Myr.

The authors found that 213 (81%) of the 263 X-ray sources have optical and/or infrared counterparts, most, but probably not all, of which are likely to be member stars of NGC 2264. There are 51 X-ray sources that lack optical or infrared counterparts: the authors believe that these are most likely extragalactic objects (active galaxies).


Catalog Bibcode

2004AJ....127.2659R

References

CHANDRA X-ray observations of young clusters. I. NGC 2264 data.
    Ramirez S.V., Rebull L., Stauffer J., Hearty T., Hillenbrand L., Jones B.,
    Makidon R., Pravdo S., Strom S., Werner M.
   <Astron. J., 127, 2659-2673 (2004)>
   =2004AJ....127.2659R

Provenance

This table was created by the HEASARC in February 2007 based on CDS table J/AJ/127/2659, files table1.dat, table4.dat and table5.dat.

Parameters

Source_Number
A running source number in order of increasing J2000 Right Ascension.

Name
The name of the Chandra X-ray source using the 'CXORRS J' prefix (Chandra X-ray Observatory, Ramirez, Rebull and Stauffer) registered with the CDS Dictionary of Astronomical Nomenclature and the J2000 coordinates of the source in the standard HHMMSS.s+DDMMSS format.

Alt_Name
The alternative name for the X-ray source using the'[RRS2004] NGC 2264' prefix recommended by the CDS Dictionary of Astronomical Nomenclature and the X-ray source number.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.01 seconds of time in the original table. The original Chandra positions were offset from their counterpart I_C band positions in the authors' optical/IR catalog of NGC 2264 stars by mean values of -0.74" +/- 0.20" in RA and +0.14" +/- 0.20" in Declination. The Chandra positions given here have been corrected for these mean offsets.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.001 arcseconds in the original table. The original Chandra positions were offset from their counterpart I_C band positions in the authors' optical/IR catalog of NGC 2264 stars by mean values of -0.74" +/- 0.20" in RA and +0.14" +/- 0.20" in Declination. The Chandra positions given here have been corrected for these mean offsets.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Off_Axis
The off-axis angle, phi, of the X-ray source from the nominal pointing direction of 6 40 48, +9 51 (J2000 RA and Dec), in arcminutes.

Extraction_Radius
The count extraction radius R_ext for the X-ray source, in arcseconds. This was different for each source, given the variation of the point spread function (PSF) across the Chandra FOV. Feigelson et al. (2002, ApJ, 574, 258) defined the 95% and 99% encircled energy radii, R(95%EE) and R(99%EE), respectively, as functions of the off-axis angle in their footnote 12. The present authors set R_ext equal to R(95%EE), except for sources with higher than 1000 counts, for which they enlarged R_ext to be equal to R(99%EE).

PSF_Fraction
The enclosed fraction of the PSF (f_PSF) used in the count rate computation, as discussed in Section 3.1 of the published reference.

Exposure
The effective exposure time t_eff of the X-ray source, in seconds. This is the exposure time corrected to account for a 1.3% loss due to readout and scaled to the effective area within the extraction radius (R_ext) with respect to the effective area on the optical axis.

Count_Rate
The net background- and vignetting-corrected count rate of the X-ray source, in counts per second. This was calculated using the formula CR = NC/(f_PSF * t_eff), where NC is the net counts and is defined as NC = (C_ext - B * pi * R_ext^2), where C_ext is the actual number of extracted counts from the source region and B is the computed background counts in counts per square arcsecond.

Flux
The flux of the X-ray source in the 0.3 to 8.0 keV energy range, in ergs/cm^2/s. The authors used the X-ray fluxes of the 14 brightest sources (excluding S Mon, source number 196) calculated from spectral fits using 2-T XSMEKAL coronal emission models to compute an X-ray flux weighted conversion factor between count rate and X-ray flux of 6.16 +/- 0.13 x 10^-15 (erg/cm^2/s)/(counts/ks) which was then used to calculate the values listed herein.

Log_Lx
The logarithm of the X-ray luminosity, in units of ergs/s, for the X-ray source, using the X-ray flux and an assumed distance of 760 pc to NGC 2264.

Prob_Constant
The constant-source probability P_c as derived from the chi-squared value comparing the data with a constant light curve, in percent. Sources with P_c < 90% are the most likely to be variable. See Section 3.3 of the published paper for more details on the variability analysis.

Comment_Flags
Flags for additional comments about the specific X-ray source, mostly concerning their variability, as follows:

        v = Variable star
        f = Flarelike light curve
        p = Possible flare in the light curve
        s = Steady increase or decrease in the light curve
        g = Galaxy
  

Ctrpart_Name
The optical and/or infrared name of the counterpart for the X-ray source. The authors constructed their optical/IR catalog by combining their original UBV(RI)c survey from Rebull et al. (2002, Cat. <J/AJ/123/1528>) (objects with "R" names) with other published catalogs. If optical photometry and/or spectral types were not available in Rebull et al. (2002), they took photometry from Park et al. (2000AJ....120..894P), Flaccomio et al. (1999, Cat. J/A+A/345/521), or Sung et al. (1997AJ....114.2644S) in that order. To find sources using Simbad nomenclature, notice that (i) the object 'Walker 143' is given as 'NGC 2264 143' in Simbad, (ii) objects with names of the form 'R NNNN' as 'CL* NGC 2264 RMS NNNN' in Simbad, and objects with names like 'Sung NNNN' from Sung et al. (1997AJ....114.2644S) are not yet in Simbad.

RA_Ctrpart
The Right Ascension of the optical/IR counterpart to the X-ray source, in (fixed) J2000 coordinates.

Dec_Ctrpart
The Declination of the optical/IR counterpart to the X-ray source, in (fixed) J2000 coordinates.

Umag
The U-Band magnitude of the optical counterpart to the X-ray source.

Umag_Flag
This flag parameter is set to 'c' to indicate that the U-band photometry for this object is contaminated by a saturated column.

Bmag
The B-Band magnitude of the optical counterpart to the X-ray source.

Bmag_Flag
This flag parameter is set to 'c' to indicate that the -band photometry for this object is contaminated by a saturated column.

Vmag
The V-Band magnitude of the optical counterpart to the X-ray source.

Vmag_Flag
This flag parameter is set to 'c' to indicate that the -band photometry for this object is contaminated by a saturated column.

Rc_Mag
The Cousins R-Band magnitude of the optical/infrared counterpart to the X-ray source.

Rc_Mag_Flag
This flag parameter is set to 'c' to indicate that the R_c-band photometry for this object is contaminated by a saturated column.

Ic_Mag
The Cousins I-Band magnitude of the optical/infrared counterpart to the X-ray source.

Ic_Mag_Flag
This flag parameter is set to 'c' to indicate that the I_c-band photometry for this object is contaminated by a saturated column.

Jmag
The 2MASS or Rebull et al. J-Band magnitude of the optical/infrared counterpart to the X-ray source.

Jmag_Flag
This flag parameter for the J magnitude has the following non-blank values:

        a = Photometry from 2MASS (<VII/233>) Extended Source Catalog
        b = Photometry contaminated by a diffraction spike
        c = Photometry contanimated by a saturated column
  

Hmag
The 2MASS or Rebull et al. H-band magnitude of the optical/infrared counterpart to the X-ray source.

Hmag_Flag
This flag parameter for the H magnitude has the following non-blank values:

        a = Photometry from 2MASS (<VII/233>) Extended Source Catalog
        c = Photometry contanimated by a saturated column
  

Kmag
The 2MASS or Rebull et al. K-Band magnitude of the optical/infrared counterpart to the X-ray source.

Kmag_Flag
This flag parameter for the K magnitude has the following non-blank values:

        a = Photometry from 2MASS (<VII/233>) Extended Source Catalog
        c = Photometry contanimated by a saturated column
  

Alt_Name_1
The Rebull et al. Catalog name of the optical/infrared counterpart to the X-ray source, using the 'R' prefix. Objects with names of this form ('R NNNN') are referred to as 'CL* NGC 2264 RMS NNNN' in Simbad.

Alt_Name_2
The Sung et al. Catalog name of the optical/infrared counterpart to the X-ray source, using the 'Sung' prefix. Objects with names of this form ('Sung NNNN') are from Sung et al. (1997AJ....114.2644S); they are not yet in Simbad.

Alt_Name_3
The 2MASS name of the optical/infrared counterpart to the X-ray source.

Other_Names
Other names for the optical/infrared counterpart to the X-ray source, as follows:

    Ogura = Ogura, 1984PASJ...36..139O, KHA NNN in Simbad
   Walker = Walker, 1956ApJS....2..365W, NGC 2264 NNN
      VSB = Vasilevskis et al., 1965AJ.....70..797V, Cl* NGC 2264 Vas NNN
       FX = Flaccomio et al., 2000, cat. <J/A+A/355/651>, [FMS2000] XNNN
      HBC = Herbig & Bell, 1988, Cat. <V/73>, HBC NNN
   Herbig = Herbig, 1954ApJ...119..483H, Em* LkHA NN
  

Contact Person

Questions regarding the NGC2264CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 21-Feb-2007